The present invention is related to a novel process for preparing certain piperidine derivatives which are useful as antihistamines, antiallergy agents and bronchodilators [U.S. Pat. No. 4,254,129, Mar. 3, 1981, U.S. Pat. No. 4,254,130, Mar. 3, 1981 and U.S. Pat. No. 4,285,958, Apr. 25, 1981].
These piperidine derivatives can be described by the following formulas: ##STR1## wherein
R.sub.1 represents hydrogen or hydroxy;
R.sub.2 represents hydrogen; or
R.sub.1 and R.sub.2 taken together form a second bond between the carbon atoms bearing R.sub.1 and R.sub.2 ;
n is an integer of from 1 to 5;
R.sub.3 is --CH.sub.2 OH, --COOH or --COOalkyl wherein the alkyl moiety has from 1 to 6 carbon atoms and is straight or branched;
each of A is hydrogen or hydroxy; and
pharmaceutically acceptable salts, hydrates and individual optical isomers thereof.
The novel process for preparing the piperidine derivatives of formula (I) and formula (II) of the present invention offers high yields and ease of purification.